How to log Python code memory consumption?

Question

Hi, I am runnin' a Docker container with a Python application inside. The code performs some computing tasks and I would like to monitor it's memory consumption using logs (so I can see how different parts of the calculations perform). I do not need any charts or continous monitoring - I am okay with the inaccuracy of this approach.

How should I do it without loosing performance?

Using external (AWS) tools to monitor used memory is not suitable, because I often debug using logs and thus it's very difficult to match logs with performance charts. Also the resolution is too small.

Setup

• using python:3.10 as base docker image
• using Python 3.10
• running in AWS ECS Fargate (but results are similar while testing on local)
• running the calculation method using asyncio

I have read some articles about tracemalloc, but it says it degrades the performance a lot (around 30 %). The article.

Tried methods

I have tried the following method, however it shows the same memory usage every time called. So I doubt it works the desired way.

Using resource

import asyncio
import resource
# Local imports
from utils import logger


def get_usage():
    usage = round(resource.getrusage(resource.RUSAGE_SELF).ru_maxrss / 1000 / 1000, 4)
    logger.info(f"Current memory usage is: {usage} MB")

    return usage


# Do calculation - EXAMPLE
asyncio.run(
  some_method_to_do_calculations()
)

Logs from Cloudwatch

Using psutil (in testing)

import psutil
# Local imports
from utils import logger


def get_usage():
    total = round(psutil.virtual_memory().total / 1000 / 1000, 4)
    used = round(psutil.virtual_memory().used / 1000 / 1000, 4)
    pct = round(used / total * 100, 1)
    logger.info(f"Current memory usage is: {used} / {total} MB ({pct} %)")

    return True

It seems like using psutil fits my needs pretty good. Thanks to all commenters! 🙏

Example

import psutil
# Local imports
from utils import logger


def get_usage():
    total = round(psutil.virtual_memory().total / 1000 / 1000, 4)
    used = round(psutil.virtual_memory().used / 1000 / 1000, 4)
    pct = round(used / total * 100, 1)
    logger.info(f"Current memory usage is: {used} / {total} MB ({pct} %)")

    return True

Fargate is using cgroup for memory limiting.

As mentioned here and here, the CPU/memory values provided by /proc refer to the host, not the container.

As a result, userspace tools such as top and free report misleading values.

You can try with something like:

with open('/sys/fs/cgroup/memory/memory.stat', 'r') as f:
    for line in f:
        if 'hierarchical_memory_limit ' in line:
            memory_limit = int(line.split()[1])
        if 'total_rss ' in line:
            memory_usage = int(line.split()[1])                     

percentage=memory_usage*100/memory_limit